Consumers use a wide range of devices and networks, including cellular phones, paging devices, personal communication services (PCS) systems, and wireless data networks. Wireless service providers create new markets for wireless devices and expand existing markets by making wireless devices and services cheaper and more reliable. Wireless service providers attract new customers by reducing infrastructure costs and operating costs, by increasing handset battery life, and improving quality of service, and new and better features.
Inadequate coverage is a persistent problem in the quality of service of any wireless network. Natural and man-made obstacles frequently create radio frequency (RF) “holes” in the coverage area of a wireless network. Voice and data call connections are frequently dropped when a wireless terminal, such as a cell phone or a similar mobile station, enters an RF hole. Mobile stations that are already in an RF hole may not be able to reliably establish new connections. Typical areas in which RF holes occur include underground tunnels, buildings that have large footprints, tall buildings, and underground shopping malls.
Wireless service providers may attempt to improve coverage by deploying RF repeater transceivers. A variety of repeaters have been developed to improve the coverage of wireless networks. In U.S. patent application Ser. No. 09/998,238 (Publication No. 20030104781), Son describes a residential wireless repeater that achieves isolation between transmit and receive antennas by physical separation of the antennas. The repeater disclosed by Son requires two separate modular repeaters that communicate simultaneously with each other with low radio frequency.
In U.S. Pat. No. 6,731,904, Judd describes a modular repeater that includes a housing having a pair of substantially 180° oppositely facing surfaces. At least one antenna element is mounted to each of these surfaces for radiating energy in a direction opposite that of another antenna element mounted to the other surface. An electronic circuit within the housing operatively couples signals between at least one antenna element on each of the oppositely facing surfaces of the module housing.
In U.S. Pat. No. 6,697,603, Lovinggood et al. describe a digital repeater for receiving and retransmitting radio frequency (RF) signals. The Lovinggood repeater down-converts a received RF signal to an intermediate frequency (IF) signal, converts the IF signal into a digital signal, processes and amplifies the digital signal into an amplified signal using the digital signal processor, and converts the amplified signal into an analog signal. The Lovinggood repeater then up-converts the analog signal to an outgoing RF signal suitable for antenna transmission.
In U.S. Pat. No. 6,640,112, Lee et al. describe a repeating method for a wireless communication system which provides time and space diversities. The method of repeating a forward link communication signal for a wireless communication system includes the steps of: a) transmitting the forward link communication signal through a first transmitting antenna; b) delaying the forward link communication signal for a predetermined time period; and c) transmitting a delayed forward link communication signal which is generated by step b) through a second transmitting antenna.
In U.S. Pat. No. 4,283,795, Steinberger presents an adaptive cross-polarization cancellation arrangement in which a first desired polarized signal and a second interfering orthogonally polarized signal, including cross-polarization components, are concurrently received at an antenna. The orthogonally polarized components of the received signal are separated and transmitted along separate paths and recombined after the phase and amplitude of the separated polarized interfering signal sample have been adjusted for maxim cancellation of cross-polarization components in the other path.
Each of the prior art repeaters described above requires at least one of the following: i) physical separation of primary and secondary antenna sets by a significant distance to reduce the magnitude of the transfer function H such that H<1/G, where G is the repeater power gain; ii) precise adjustment of input-output phase adjustment embodied in H such that the vector product G*H is <0 in order to yield negative feedback; iii) separate modules for the reception of external signals and the retransmission of signals internal to the building; and iv) methods for the cancellation of multiple time-delayed echoes that would occur in a home or in-building environment with multiple scattering surfaces. The prior art repeaters generally do not provide a method of canceling any echoes from the output that would lead to unstable operation (i.e., oscillations).
Therefore, there is a need in the art for improved repeaters for use in wireless networks. In particular, there is a need for a repeater that cancels echoes and avoids oscillation.